title: Activatable aptamer probe for contrast-enhanced in vivo cancer imaging based on cell membrane protein-triggered conformation alteration.
abstract: Aptamers have emerged as promising molecular probes for in vivo cancer imaging, but the reported "always-on" aptamer probes remain problematic because of high background and limited contrast. To address this problem, we designed an activatable aptamer probe (AAP) targeting membrane proteins of living cancer cells and achieved contrast-enhanced cancer visualization inside mice. The AAP displayed a quenched fluorescence in its free state and underwent a conformational alteration upon binding to target cancer cells with an activated fluorescence. As proof of concept, in vitro analysis and in vivo imaging of CCRF-CEM cancer cells were performed by using the specific aptamer, sgc8, as a demonstration. It was confirmed that the AAP could be specifically activated by target cancer cells with a dramatic fluorescence enhancement and exhibit improved sensitivity for CCRF-CEM cell analysis with the cell number of 118 detected in 200 μl binding buffer. In vivo studies demonstrated that activated fluorescence signals were obviously achieved in the CCRF-CEM tumor sites in mice. Compared to always-on aptamer probes, the AAP could substantially minimize the background signal originating from nontarget tissues, thus resulting in significantly enhanced image contrast and shortened diagnosis time to 15 min. Furthermore, because of the specific affinity of sgc8 to target cancer cells, the AAP also showed desirable specificity in differentiating CCRF-CEM tumors from Ramos tumors and nontumor areas. The design concept can be widely adapted to other cancer cell-specific aptamer probes for in vivo molecular imaging of cancer.
authors.affiliation: State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Institute of Biology, Hunan University, Changsha, China 410082.
authors.forename: Hui
authors.initials: H
authors.lastname: Shi
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: He
authors.forename: Kemin
authors.initials: K
authors.lastname: Wang
authors.forename: Xu
authors.initials: X
authors.lastname: Wu
authors.forename: Xiaosheng
authors.initials: X
authors.lastname: Ye
authors.forename: Qiuping
authors.initials: Q
authors.lastname: Guo
authors.forename: Weihong
authors.initials: W
authors.lastname: Tan
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Qing
authors.forename: Xiaohai
authors.initials: X
authors.lastname: Yang
authors.forename: Bing
authors.initials: B
authors.lastname: Zhou
mesh_terms: D052157:Aptamers, Nucleotide; D001483:Base Sequence; D002460:Cell Line; D015342:DNA Probes; D005434:Flow Cytometry; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
chemical_list: D052157:Aptamers, Nucleotide; D015342:DNA Probes; D008565:Membrane Proteins